Question:
Which antibiotic undergoes light catalysed autoxidation:
Which antibiotic undergoes light catalysed autoxidation:
Updated On: Jul 14, 2026
- Polyene antibiotics
- Beta lactum antibiotics
- Sugar derived antibiotics
- Macrolide antibiotics
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The Correct Option is A
Approach Solution - 1
The correct option is (A): Polyene antibiotics.
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The question asks which antibiotic class breaks down mainly through oxidation triggered by exposure to light. Let's check each class against its known chemical structure and degradation pathway.
- Polyene antibiotics: Drugs such as amphotericin B and nystatin carry a long chain of conjugated carbon-carbon double bonds. This extended conjugation absorbs light readily and reacts with atmospheric oxygen, undergoing light-catalysed autoxidation that breaks down the conjugated system and destroys antifungal activity, which is why these drugs must always be protected from light.
- Beta lactum antibiotics: The reactive part of penicillins and cephalosporins is a strained four-membered lactam ring that is unstable to moisture and to enzymes like beta-lactamase, not photochemically reactive in the way a conjugated polyene system is.
- Sugar derived antibiotics: Aminoglycosides and other sugar-based antibiotics degrade mainly through hydrolysis of their glycosidic bonds rather than through light-driven oxidation of double bonds, since they don't carry an extended conjugated chromophore.
- Macrolide antibiotics: Macrolides such as erythromycin are built around a large lactone ring and are chiefly unstable in acidic conditions, where the ring undergoes internal rearrangement, rather than being especially prone to light-catalysed oxidation.
Only the polyene class has the extended conjugated double bond system needed to absorb light and undergo autoxidation.
The correct answer is Polyene antibiotics.
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